Two men and a woman were killed Monday when a shooter opened fire on a tram in Utrecht. Authorities put the Netherlands' fourth largest city in lockdown for hours amid fears that more than one shooter was active at different locations.

The terror alert level also was raised from four to the maximum five while police hunted for the shooter. It was dropped to four once the suspect was detained.

Prosecutors have said they were focused on a possible terrorist motive because of the nature of the shooting — they say none of the victims was known to the alleged shooter — and because of a note found in a getaway car. They have not disclosed what was written in the note.

Photo credit: NBC News

A silent march is planned for Friday evening in Utrecht to commemorate the victims.